Field of the Invention
The present invention relates to an engine system having a coolant control valve that can improve overall cooling efficiency and reduce fuel consumption by controlling both a coolant supplied to a cylinder block and a coolant discharged from a cylinder head.
Description of Related Art
Engines produce torque by burning a fuel to create engine, and discharge surplus thermal energy. Particularly, a coolant absorbs thermal energy as it circulates through an engine, a heater, and a radiator, and releases the thermal energy.
Oil becomes highly viscous at low engine coolant temperatures. With thick oil, friction and fuel consumption increase, and exhaust gas temperatures rise gradually, lengthening the time taken for catalyst activation and causing deterioration in exhaust gas quality. Moreover, it takes a long time to get a heater to function normally, so passengers and a driver will feel cold.
When the engine coolant temperature is excessively high, knocking may occur. If ignition timing is adjusted to suppress knocking, the engine performance may be degraded. In addition, excessive lubricant temperatures may result in poor lubrication.
However, one coolant control valve is used in specific regions of an engine, and is a valve that controls a number of cooling elements, like keeping the coolant at high temperatures and other regions at low temperatures.
Even with the use of one coolant control valve, an outlet control method for controlling coolants discharged from an engine (a cylinder block and a cylinder head) and an inlet control method for controlling coolants supplied to the engine are generally used.
The outlet control method is vulnerable to abrupt changes in water temperature, exhibits low precision in temperature control, and can decrease the durability of the coolant control valve. Also, the inlet control method works against the cavitation of high-temperature coolants and needs a complicated cooling system structure.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.